Re: coherers

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>

>         Did you use magnetic stainless which could be separated with a
magnet?

Yes. From a stainless steel coin, that is magnetic. (Stainless steel is
always magnetic.)

> My experience with stainless steel has been that it's very hard to file,
> and I never considered it for a coherer because of that. 

Easy with a grinding wheel.

> Have you made
> any relative sensitivity measurements for various materials?  Also, what
> did you use for the end plugs?  In reading the old literature I see that
> materials different from the filings were used most of the time, but I'm
> not sure if that really matters or not.  I've wondered if the "cohering"
> is due to breakdown of very thin oxide layers on the plugs or the
> filings, and with stainless steel there shouldn't be significant oxide
> layers and the action would have to be due to minute air gaps in the
> filings.  Have you given the matter any serious thought?

I didn't make systematic measurements of sensitivity. The stainless
steel coherer performed better, but was smaller than the regular steel
coherer. Sensitivity varies, as the device changes when tapped for
"decoherence". I have seen values from 3 V to 30 V with the same
coherer.

Have you read something about the "spin transistor"? The device is 
composed of two layers of magnetic material separated by a thin 
insulation. When the magnetizations on both layers are in different
directions, current doesn't flow, but when they are identical some 
current flows, as electrons with the same spin easily tunnel across 
the insulation. This description looks a lot as what may happen
between the grains of a coherer. A spin transistor ahead of time?
(Ok, coherers work also with nonmagnetic metals, but all metals are
a bit magnetic, and who knows what quantum effects happen at the 
microscopic boundaries of the grains?)
 
>         The coherers I have built here all have exhibited essentially
infinite
> resistance in the OFF state, and resistance from a couple of hundred
> ohms down to less than 10 ohms in the ON state.  I use an ordinary
> transistor curve tracer and look at the current/voltage in only one
> quadrant.  Typical "breakdown voltage" is of the order of 5 volts.
> Something I almost always observe is that the ON resistance drops to
> lower and lower values as the input excitation is repeated.  For
> "playing around" I just use a piezoelectric sparker in the vicinity of
> the coherer which works well.  [The coherer is connected to the
> measuring circuit through 1 mH series inductors in both sides.]  I also
> have a small hand held spark transmitter with an 8 inch vertical
> "antenna", with which I've been able to get the coherer with similar
> antennas to turn ON at a distance of as much as 40 feet.  I don't know
> how to estimate the voltage or power which triggers the coherer under
> those conditions.

My coherers behave as you describe. I used a signal generator to produce
thin pulses applied to a biased coherer (a resistor and a battery)
through 
a capacitor, and observed what was happening with the voltage over the 
coherer with an oscilloscope. The thinnest pulses that could generate 
triggered the coherers, and the transition to conduction always took
less 
than 10 ns. DC triggers them too. 

I can trigger a coherer with an electrostatic machine, by just turning
it without producing sparks, at short distances. A Leyden jar discharge
triggers a coherer circuit without a special antenna several meters
away.
Curiously, I tried to excite the same coherer with the spark from an
induction coil. I found that for the same spark length, and even using
an antenna, the static machine produces a better result. The difference 
that is observed with an oscilloscope over the coherer is just of
frequency content (higher frequencies from the static machine). 
I didn't try the coherers with a Tesla coil yet. A cell phone does't
trigger a coherer (too high frequency, or too low power?).

> I find the Radicon toys mentioned on the web as
> "collectibles", but haven't been able to learn anything more about the
> coherer and how it was made.

Could you make a picture of the Radicon coherer available? The relay 
would be interesting to see too.

Antonio Carlos M. de Queiroz